Isocyanate is a functional group having the formula R—N═C═O. A molecule which contains more than one isocyanate groups is referred to as a polyisocyanate (diisocyanate, triisocyanate, etc.). Isocyanates are generally highly reactive.
Isocyanates are capable of forming polyurethanes or polyureas when reacted with molecules containing one or more hydroxyl functional groups (e.g., alcohol, polyols, etc.) or amino functionality (—NH2) such as in polyamines to form polyureas. A typical reaction resulting in the formation of a polyisocyanate with an alcohol to form a polyurethane is shown below:

Polyurethanes can be used as implantable material either as implants either preformed and then implanted into the target tissue site or as a flowable material that is implanted at the site, where the polyurethane adheres and/or hardens at the target tissue site (e.g., tissue defect, bone defect, etc.). In some embodiments, the polyurethane is porous and allows cells into the site to aid in remodeling and repair of the defect, where it can then degrade over time (e.g., 2 weeks to 6 months or longer).
To make polyisocyanates, phosgene (COCl2) can be used. Phosgene is a valued industrial reagent and building block in the synthesis of pharmaceuticals and other organic compounds. However, phosgene is toxic and great care should be used in its handling.
There is a need for new methods and compositions to efficiently and safely make polyisocyanates. Methods and compositions that can efficiently and safely generate phosgene are also needed.